This blog post contains my technical opinion and is for general information purposes only. Your local Authority Having Jurisdiction may have a different interpretation, so please confirm your AHJ’s position prior to using this information. Please refer to the latest CE Code version for guidance on cable usage.
In my last blog post, I covered the standards, applications, and pros & cons of Type TC tray cables. Now I’ll address their installation. In the mid-1990s, there was a push by the petrochemical industry to update the CE Code to allow tray cables for use in their projects. Initially, there was some mixed resistance to incorporating this new cable type in the CE Code, resulting in restrictive code rules around tray cable installations.
Confusion over what to do when the tray cable leaves the cable tray resulted in tray cables initially being slow to catch on. CE Code rule 12-2202(2) required Type TC tray cable to be installed in conduit, suitable raceway, or direct buried when not in the cable tray and provided with mechanical protection where subject to damage. With cost savings being one of the determining factors to using a tray cable over a Teck90 cable, these additional mechanical protection systems could add significant installation costs. How to meet these requirements was open to a lot of interpretation, sometimes resulting in elaborate welded protection systems, negating any cost savings from the cables.
In Alberta, where variances are used, the petrochemical industry worked around these code limitations via “Protection by Location” CE Code variances. A “Request for Variance” is an AB permitting process to deviate from CE Code safety requirements based upon a technical argument of how you plan to deviate from a CE Code rule and maintain a safe installation for a specific project. In other provinces, special permission would be required per the local AHJ. Over the course of several projects, they learned how to safely install and protect tray cables, minimizing additional protection costs via “Protection by Location” routings.
“Protection by Location” involves routing cables in areas that are typically not subjected to mechanical damage as they are mechanically protected by the location in which they are installed.
When using “Protection by Location” to run tray cables it is good practice to involve all the project stakeholders early in the process to create buy-in and clarify intentions. One method is to create shop drawings clarifying specific applications with acceptable routing methods and host early meetings with all the stakeholders so that early agreement can be achieved on installation methods. Involve design, construction, contractor, operations, and quality control departments to prevent installation methods from being questioned in the middle of the project. It’s always easier to achieve consensus early in the project rather than during construction.
CSA tray cable standard, C22.2 #230-17, now allows for 2 types of tray cables, TC and TC-ER. TC-ER tray cables are intended for extended run applications and are permitted by 12-2202 (3) to transition between cable trays, and between cable trays and utilization equipment. They can transition for 1.5m unsupported and for 7.5m when continually supported. Currently, manufacturers of CSA tray cables have very limited 300V/600V/1KV commercial TC-ER products. That leaves designers to work with TC-only rated tray cables which still require “Protection by Location” variances for practical use in their low voltage tray cable installations. Note that there are some UL TC-ER rated cables but typically, they only meet CSA TC testing. Cable manufacturers are working on CSA TC-ER rated cable product lines, so it is possible that they will become available soon. There are, however, some commercial CSA TC-ER SHD-GC mining cables as well as medium voltage cable options allowing flexible installation options per 12-2202 (3).
In summary, the CE Code and CSA products continue to progress, making tray cable installation requirements easier to meet, which maximizes project cost and labour savings. The petrochemical industry’s use of “Protection by Location” CE Code variances and involving the entire project team early in the design process can be valuable tools for other industries interested in benefiting from tray cable advantages.